Stabilized organic peroxydicarbonates compositions

Abstract

Thermally stabilized initiator composition comprising:(a) at least one dialkyl peroxydicarbonate, and(b) a stabilizing effective amount of a compound of Structure I:wherein R1 and R2 are as defined in the summary of the invention section, processes for their preparation and use are disclosed.

Description

This invention relates to compositions classified in the art of chemistry as dialkyl peroxydicarbonates, more specifically to new and novel thermally-stabilized initiator compositions comprising dialkyl peroxydicarbonates stabilized by the addition thereto of a stabilizing effective amount of at least one stabilizing compound selected from the group consisting of diesters of unsaturated dicarboxylic acids. The invention further relates to the use of such novel compositions as initiators of polymerization or cure of ethylenically unsaturated monomers, oligomers and polymers. The invention still further relates to the stabilization of dialkyl peroxydicarbonates during their manufacture by the inclusion of stabilizing effective amount of at least one stabilizing compound selected from the group consisting of non-hydrolyzable diesters of unsaturated dicarboxylic acids in the mixture of reactants from which a dialkyl peroxydicarbonate is to be prepared prior to, at the commencement of, o...

AI Technical Summary

Benefits of technology

This invention also provides a novel manufacturing process of enhanced safety for production of dialkyl peroxydicarbonates and simultaneously provides an alternate means for producing novel, stabilized dialkyl peroxydicarbonate compositions containing an amount of stabilizing compound sufficient to stabilize the dialkyl peroxydicarbonate that is from about 10 to about 90%, preferably 20 to 50% by weight on dialkyl peroxydicarbonate, of a compound of Structure I which will not hydrolyze under the reaction conditions.

The process employs a quantity (10 to 90%, preferably 20 to 50% by weight based on dialkyl peroxydicarbonate) of a compound of Structure I which will not hydrolyze under the reaction conditions during the processing for enhancing the thermal stability of the dialkyl peroxydicarbonate during manufacture, thus suppressing self-accelerating decomposition of the dialkyl peroxydicarbonate during subsequent storage and handling.

Temperatures of 25.degree. C. to 100.degree. C., preferably 30.degree. C. to 90.degree. C., more preferably 75.degree. C. and levels of novel stabilized peroxydicarbonate initiator compositions (on a pure basis) of 0.002 to 3%, preferably 0.005% to 1%, more preferably 0.01% to 0.75% by weight based on monomer (amount effective for initiation), are normally employed in conventional polymerizations and copolymerizations of ethylenically unsaturated monomers. One of skill in art will recognize that some of the above listed monomers will undergo polymerization at still lower temperatures in the presence of the peroxydicarbonates contemplated by this invention and that certain monomers, such as ethylene are conventionally polymerized at pressures greater than atmospheric. The processes contemplated by this invention include such conventional processing conditions. The novel stabilized peroxydicarbonate compositions of this invention can be used in combination with other free-radical initiators such as those disclosed at the bottom of column 4 and the top of column 5 of U.S. Pat. No. 4,525,308. Using the peroxide compositions of this invention in combination with these initiators adds flexibility to the processes of polymer producers and permits them to "fine tune" their polymerization processes.

It is important in the preparation of PVC compounds intended for food contact application that undesirable extractable residues from reaction of polymerization catalysts and polymerization catalyst stabilizers be avoided.

The ADC resin compositions described above can be filled with various materials, such as antioxidants (AO's), heat, ultraviolet (UV) and light stabilizers, tints, photochromic additives and dyes. In addition, the ADC resin compositions can contain additives such as acrylic polymers and the anti-shrink, low molecular weight acrylic resins disclosed in U.S. Pat. No. 4,217,433. Such anti-shrink additives are employed to counter the 14% shrinkage that occurs when ADC monomer is polymerized.

Problems solved by technology

Generally, dialkyl peroxydicarbonates which are in liquid form (molten or in solution) above ca. 10. degree. c. are very hazardous owing to auto-accelerated decomposition attributed to induced decomposition of the dialkyl peroxydicarbonate.

However, when such stabilizing compositions are used to polymerize vinyl chloride monomer (VCM), there is potential for contamination of the resulting PVC resin by the additives.

This contamination is undesirable, both for the PVC resin as well as for the environment.

However, polymer producers such as PVC producers do not like to employ initiators containing significant levels of hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide since these impurities are free-radical chain-transfer agents and can become incorporated into the resin molecular chains as peroxy end groups.

Such labile end groups can adversely affect the thermal and color stability of the resin.

In addition, the lower molecular weight t-alkyl hydroperoxides such as t-butyl and t-amyl hydroperoxides are sufficiently volatile to cause problems during recycle of vinyl chloride and other monomers.

Polymer producers, such as polyvinylchloride manufacturers prefer not to use initiators stabilized with compounds having ethylenic unsaturation conjugated with acetylenic or nitrile groups, such as acrylonitrile or methacrylonitrile due to toxicity and waste water concerns.

These compounds are toxic and / or carcinogenic and would require special waste water handling and permits.

However, the addition of such higher half-life peroxides can cause problems during the recycle of vinyl chloride or other monomers and can cause gel formation during stripping of the resin.

However, polymer producers, including polyvinylchloride manufacturers do not like to employ peroxides stabilized using these materials since their use introduces impurities which can cause toxicity and quality problems in the final resin.

The dibutyl maleate will have decreased the shock sensitivity as mentioned in the two aforementioned patents, but did not increase the safety characteristics of the peroxyesters.

The above two patents also disclose that any solvent will reduce shock sensitivity but that some will also have a deleterious effect on properties of the polymer produced.

Solid diluents may interfere with aqueous separations and many of the proposed compounds will hydrolyze under peroxide production conditions leaving pure unstabilized peroxide in the reactor at elevated temperatures; an extremely dangerous and undesirable state.

Furthermore, the organic peroxides disclosed in these patents are no longer considered shock sensitive by today's standard test methods.

During this quiescent period the organic dialkyl peroxydicarbonate phase is deprived of oxygen stabilizer and a hazardous self-accelerating decomposition of the liquid dialkyl peroxydicarbonate phase can occur.

Images